Introduction: We describe a simple and rapid screening test for basic financial knowledge that is suitable for administration to people with mild intellectual disabilities. Method: The Coins and Costs test asks respondents to name coins, and to estimate prices of objects ranging between 1 British Pound (an ice cream) and 100K British Pounds (a small house). The test was administered, alongside a battery of neuropsychological tests, to 40 people attending day services (mean Full-Scale IQ = 59.1). Results: Total scores were normally distributed, and correlated significantly with receptive language ability and performance on memory tests, but not with IQ or executive functioning. Conclusion: The test provides a rapid (less than 5 min) screening test that has good psychometric properties and appears very suitable for assessing basic financial knowledge of people with mild intellectual disabilities.